Higenamine is an Amniti tuber derived compound whose chemical structure is 1-(4´-hydroxybenzyl)-6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline containing catechol ring and tetrahydroisoquinoline nucleus in its own structure, both of which are well known to have agonistic effects on adrenergic receptors. Using guinea-pig atria(rich in β₁-receptor) and treachea(rich in /β₂-receptor), we studied pharmacological actions of higenamine on these organs with special interest of its relevancy of β-receptor selectivity. In order to further clarify its pharmacological characteristics, the influncences of pretreatment of reserpine or cocaine were also investigated. The results were summarized as follows :
1. Higenamine had remarkable chronotropic, inotropic and bronchodilator effects in guinea-pig spontaneously beating right atria, left atria and trachea, in dose-dependent manners.
2. All of above actions were blocked competitively by propianolol, which shows nonselectivity of higenamine on (β-receptors. pA₂propranolol against higenamine were 7.93, 7.76 and 8.46 in guinea-pig right atria, left atria and treachea, respectively.
3. Reserpine pretreatment(5㎎/㎏, ip, 24h) did not show my decrease in pharmacological actions of higenamine, which suggests higenamine has direct action on β-receptor not via catecholamine release.
4. Cocaine pretreatment(1μM) had no influence on pharmacological actions of higenamine in contrast with nor epinephrine, which suggests there is no neuronal uptake mechanism of higenamine in the studied organ preparations.
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